Dynamics of the hydrocarbon-degrading Cycloclasticus bacteria during mesocosm-simulated oil spills

Original research articleWe used catalysed reported deposition – fluorescence in situ hybridization (CARD-FISH) to analyse changes in the abundance of the bacterial groups Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes, and of hydrocarbon-degrading Cycloclasticus bacteria in mesocosms that had received polycyclic aromatic hydrocarbons (PAHs) additions. The effects of PAHs were assessed under four contrasting hydrographic conditions in the coastal upwelling system of the Rías Baixas: winter mixing, spring bloom, summer stratification and autumn upwelling. We used realistic additions of water soluble PAHs (approximately 20–30 μg l−1 equivalent of chrysene), but during the winter period we also investigated the effect of higher PAHs concentrations (10–80 μg l−1 chrysene) on the bacterial community using microcosms. The most significant change observed was a significant reduction (68 ± 5%) in the relative abundance of Alphaproteobacteria. The magnitude of the response of Cycloclasticus bacteria (positive with probe CYPU829) to PAHs additions varied depending on the initial environmental conditions, and on the initial concentration of added PAHs. Our results clearly show that bacteria of the Cycloclasticus group play a major role in low molecular weight PAHs biodegradation in this planktonic ecosystem. Their response was stronger in colder waters, when their background abundance was also higher. During the warm periods, the response of Cycloclasticus was limited, possibly due to both, a lower bioavailability of PAHs caused by abiotic factors (solar radiation, temperature), and by inorganic nutrient limitation of bacterial growth.This research was supported by the MEC contract IMPRESION (VEM2003-20021); an European Community Marie Curie Reintegration Fellowship (MERG-CT-2004-511937) and a Juan de la Cierva-MEC contract.Versión del editor5,84

Plant functional and taxonomic diversity in European grasslands along climatic gradients

Aim: European grassland communities are highly diverse, but patterns and drivers of their continental-scale diversity remain elusive. This study analyses taxonomic and functional richness in European grasslands along continental-scale temperature and precipitation gradients. Location: Europe. Methods: We quantified functional and taxonomic richness of 55,748 vegetation plots. Six plant traits, related to resource acquisition and conservation, were analysed to describe plant community functional composition. Using a null-model approach we derived functional richness effect sizes that indicate higher or lower diversity than expected given the taxonomic richness. We assessed the variation in absolute functional and taxonomic richness and in functional richness effect sizes along gradients of minimum temperature, temperature range, annual precipitation, and precipitation seasonality using a multiple general additive modelling approach. Results: Functional and taxonomic richness was high at intermediate minimum temperatures and wide temperature ranges. Functional and taxonomic richness was low in correspondence with low minimum temperatures or narrow temperature ranges. Functional richness increased and taxonomic richness decreased at higher minimum temperatures and wide annual temperature ranges. Both functional and taxonomic richness decreased with increasing precipitation seasonality and showed a small increase at intermediate annual precipitation. Overall, effect sizes of functional richness were small. However, effect sizes indicated trait divergence at extremely low minimum temperatures and at low annual precipitation with extreme precipitation seasonality. Conclusions: Functional and taxonomic richness of European grassland communities vary considerably over temperature and precipitation gradients. Overall, they follow similar patterns over the climate gradients, except at high minimum temperatures and wide temperature ranges, where functional richness increases and taxonomic richness decreases. This contrasting pattern may trigger new ideas for studies that target specific hypotheses focused on community assembly processes. And though effect sizes were small, they indicate that it may be important to consider climate seasonality in plant diversity studies

10 Possible Limitations of Current Ecological Theory

I make ten observations of the limitations of ecological science as I have seen it develop over the last 56 years. The key focus is on the scientific maturity of our approaches, and the constraints that flow from pretending we are physicists, that progress will come from more mathematical models, and that generality will flow from short-term studies. All of my observations may be incorrect but they might generate some useful discussion about dangerous ideas on where ecology is headed.</p